A highly selective and sensitive fluorescence chemosensor based on optically active polybinaphthyls for Hg

The chiral polymer was synthesized by the polymerization of 4,7-diethynylbenzo[2,1,3]-thiadiazole (M-1) with (R)-6,6′-dibutyl-3,3′-diiodo-2,2′-bis(diethylaminoethoxy)-1,1′-binaphthyl (R-M-1) via Pd-catalyzed Sonogashira reaction. The chiral polymer has orange fluorescence due to the extended π-electronic structure between binaphthyl unit and benzo[2,1,3]thiadiazole (BT) group via ethynyl bridge. The responsive optical properties of the polymer on various metal ions were investigated by fluorescence spectra. The fluorescence of the chiral polymer can produce the pronounced enhancement as high as 1.8-fold upon addition of 1:2 molar ratio of Hg²⁺. Compared with other cations, such as K⁺, Mg²⁺, Pb²⁺, Co²⁺, Ni²⁺, Ag⁺, Cd²⁺, Cu²⁺, Zn²⁺, Mn²⁺ and Fe³⁺, Hg²⁺ can produce the pronounced fluorescence response of the polymer. The result indicates this kind of chiral polybinaphthyls incorporating diethylamino and benzo[2,1,3]thiadiazole (BT) moieties as receptors exhibits highly sensitive and selective behavior for Hg²⁺ detection.